A hinge is often used to connect a cover with the body of a foldable apparatus. There are many foldable mobile phones using hinges to connect their bodies and covers. A foldable mobile phone usually has a smaller volume than others not foldable.
In the prior art, the maximum opening angle, defined by the cover and the body, is not adjustable. According to different demands of various users, for example, different users having different facial sizes, an adjustable maximum opening angle is required to accommodate the various users.